After each Strife there is always a period of resettlement. Hundreds and sometimes thousands of refugees are forced to relocate, there are months of looting and pillaging, new power dynamics arise in the Antiarch races, and hundreds of men and women find themselves enslaved. This period of change usually lasts a few years before everyone gets used to their new settings, or shackles as the case may be. Usually several Primarch cities have been destroyed or re-colonized, sometimes culminating in the domination of an entire continent, usually Atollia.
However, every Strife has failed to completely eliminate the empires and cities of the Primarchs. Most notably, the city of Aecheron capital of the continent of Aechre has never fallen to a Strife, though Aechre has often been dominated by the Antiarchs. For this reason Aecheron is typically a major staging ground for the massive and vengeful holy wars that have historically answered every Strife. These campaigns are called the Restorations, fueled by the resentful and displaced Primarchs as they regroup and prepare to take back their homes.
Though their populations would have dwindled due to the preceding wars, Resotrations tend to rally all the Primarch nations, no matter how insular, as well as any race, nation, or group that remained neutral during the Strife. There tends to be an understanding that the burgeoning wealth and power of the Antiarchs would eventually endanger every non-Antiarch on the planet. The conflict is also fueled by religion, as the devout take up arms to reclaim their holy shrines and places of worship.
These Restorations, taking advantage of the Antiarch’s thinned armies and stretched resources, tend to clear every kobold, orc, goblin, and wayward cultist out of the occupied lands, and usually to the fringes of known civilization. Though as it is with every Strife, every Restoration has ended long before the antagonizing race has been wiped out, making another future Strife almost certain.
However, given the diminishing time that elapses between each Strife and Restoration, it seems unlikely that the next Antiarch uprising will be a significant challenge to the various Primarch cultures of Atlas.